India has stepped up efforts to sell an advanced cruise missile system to Vietnam and has at least 15 more markets in its sights, a push experts say reflects concerns in New Delhi about China’s growing military assertiveness.

Selling the supersonic BrahMos missile, made by an Indo-Russian joint venture, would mark a shift for the world’s biggest arms importer, as India seeks to send weapons the other way in order to shore up partners’ defenses and boost revenues.

The government of Prime Minister Narendra Modi has ordered BrahMos Aerospace, which produces the missiles, to accelerate sales to a list of five countries topped by Vietnam, according to a government note viewed by Reuters and previously unreported.

The others are Indonesia, South Africa, Chile and Brazil.

Why China is worried

Recent reports confirm that India and Vietnam are once again discussing the possibilities of the sale of the BrahMos missiles; both the countries are involved in territorial disputes with China, the former over the Line of Actual Control and the latter in the South China Sea. India and Vietnam have discussed the possibility of the sale of BrahMos cruise missiles for quite some time now, but India was careful to not annoy China with any strategically destabilising move.

However, China’s ‘string of pearls’ strategy vis-a-vis India in the South Asian region, especially China’s alliance with Pakistan, its efforts to strengthen defence ties with Sri Lanka are all an annoyance for New Delhi. Moreover, India is also concerned about China’s One Belt One Road initiative.

India’s strategy over South China Sea

Vietnam is modernising its defence forces as a result of its territorial disputes with China, and India could be a crucial partner.

In May 2015, India and Vietnam signed the joint vision statement on defence cooperation from 2015-20 to bolster defence ties, including naval cooperation between the two countries

A source at the defense ministry said India was hoping to conclude negotiations on the supply of BrahMos to Vietnam by the end of the year.

The Indian government is also considering a proposal to offer Vietnam a battleship armed with the BrahMos missiles instead of just the missile battery, the source said.

“A frigate integrated with the BrahMos can play a decisive role, it can be a real deterrent in the South China Sea,” the source said, adding New Delhi would have to expand the line of credit to cover the cost of the ship.

Indian warships are armed with configurations of eight or 16 BrahMos missiles each, while sets of two or four would go on smaller vessels.

A Russian official said exports of BrahMos to third countries was part of the founding agreement of the India-Russia joint venture. Only now India had armed its own military with the BrahMos was there capacity to consider exporting, he added.